Medium-entropy alloy aerogel with in-situ grown carbon nanotubes for microwave absorption

Abstract

The application provides a medium-entropy alloy aerogel for in-situ growth of carbon nanotubes, and relates to the field of microwave absorption of nanocomposites.The application realizes in-situ growth of carbon nanotubes on a medium-entropy alloy aerogel framework through a self-combustion combined one-step reduction / catalysis method, and obtains an FCNM (FeCoNi-melamine) structure.The medium-entropy alloy aerogel framework has a large number of microporous structures, so that more electromagnetic waves enter the structure interior and are gradually attenuated through multiple reflections; the carbon nanotubes have excellent electric conductivity, so that the induced current generated by electromagnetic waves is dissipated in the form of Joule heat in the process of current conduction. Due to the magnetic-electric coupling effect of the carbon nanotubes and the medium-entropy alloy framework, suitable dielectric constant and magnetic permeability can be obtained by adjusting the length of the carbon nanotubes, so that the composite material has excellent impedance matching and electromagnetic wave absorption performance.

Description

Technical Field

[0001] This invention relates to the field of microwave absorption technology, and more specifically to a medium-entropy alloy aerogel with in-situ grown carbon nanotubes for microwave absorption. Background Technology

[0002] The development of the information age encompasses fields such as mobile communications, transportation, aerospace, and the military, with significant breakthroughs achieved in technologies such as 5G, artificial intelligence, and artificial satellites. These technologies have placed higher demands on the size and operating speed of electronic devices. However, these smaller, more technologically advanced industrial devices generate electromagnetic waves during operation, posing certain safety risks to some equipment.

[0003] However, most microwave absorbing materials currently on the market are designed for medium and high frequency microwaves and cannot meet the market demand for low frequency microwave absorption. Moreover, most of the few low frequency microwave absorbing materials have the defects of high density and high quality (such as metallic materials).

[0004] Therefore, it is urgent to develop a low-density microwave absorbing material for medium and low frequencies. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a medium-entropy alloy aerogel with in-situ grown carbon nanotubes for microwave absorption, which solves the technical problem of high density and high quality in low-frequency absorbing materials in existing technologies.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a medium-entropy alloy aerogel with in-situ grown carbon nanotubes for microwave absorption. The preparation method of the medium-entropy alloy aerogel with in-situ grown carbon nanotubes for microwave absorption includes:

[0008] A multi-metal solution with a total metal ion concentration of 0.1 mol / L was prepared; the multi-metal solution was composed of a mixture of Ni(NO3)2·6H2O, Co(NO3)2·6H2O and Fe(NO3)3·9H2O; the multi-metal solution contained Ni 2+ Co 2+ Fe 3+ The mole ratio is 5:3:2;

[0009] A gelling agent was added to a multi-metal solution, and the mixture was stirred magnetically until homogeneous to obtain a solution; the molar ratio of the gelling agent to nitrate was 3:5.

[0010] The mixture is heated to boil and evaporate to obtain a gel layer; the gel layer is then heated until it comes to rest to obtain a NiCoFe metal oxide aerogel.

[0011] The obtained NiCoFe metal oxide aerogel was placed in ceramic boat A, and melamine powder was weighed into ceramic boat B.

[0012] Place ceramic boat A in the downstream part of the high-temperature tube furnace and ceramic boat B in the upstream part of the high-temperature tube furnace. Assemble the high-temperature tube furnace, slowly introduce protective gas, anneal at high temperature, and then cool to room temperature to obtain the medium-entropy alloy aerogel of in-situ grown carbon nanotubes for microwave absorption.

[0013] Furthermore, the gelling agent is glycine.

[0014] Furthermore, the protective gas comprises 5% H2 and 95% Ar.

[0015] Furthermore, the cooling to room temperature after high-temperature annealing specifically involves: heating to 700°C within 230 minutes, holding at that temperature for 6 hours, and then cooling to room temperature within 100 minutes.

[0016] Furthermore, the mass ratio of NiCoFe metal oxide aerogel placed in ceramic boat A to melamine powder placed in ceramic boat B is 1:10 to 40.

[0017] Furthermore, the heating temperature for boiling and evaporating the heated mixture is 200°C.

[0018] The present invention provides a medium-entropy alloy aerogel for in-situ growth of carbon nanotubes for microwave absorption, which has the following advantages compared with the prior art:

[0019] This invention utilizes a self-combustion combined with a one-step reduction / catalysis method to in-situ grow carbon nanotubes on a medium-entropy alloy aerogel framework, resulting in an FCNM (FeCoNi-Melamine) structure. The medium-entropy alloy aerogel framework has numerous micropores, allowing more electromagnetic waves to enter the structure and gradually dissipate through multiple reflections. The carbon nanotubes possess excellent electrical conductivity, causing the induced current generated by the electromagnetic waves to dissipate as Joule heat during current conduction. Due to the magnetoelectric coupling effect between the carbon nanotubes and the medium-entropy alloy framework, suitable dielectric constant and permeability can be obtained by adjusting the length of the carbon nanotubes. Therefore, this composite material exhibits excellent impedance matching and electromagnetic wave absorption performance.

[0020] Secondly, the density of the resulting aerogel is significantly lower than that of metallic microwave absorbing materials. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A transmission electron microscope image of FCNM provided for an embodiment of the present invention;

[0023] Figure 2 The microwave absorption performance of the medium-entropy alloy aerogel with in-situ grown carbon nanotubes for microwave absorption provided in the embodiments of the present invention is shown in the range of 2-18 GHz when the melamine addition amount is 1g, 2g, 3g and 4g respectively; (corresponding to Examples 1, 2, 3 and 4).

[0024] Figure 3 The microwave absorption performance of the medium-entropy alloy aerogel with in-situ grown carbon nanotubes for microwave absorption provided in the embodiments of the present invention at 2-6 GHz with melamine addition amounts of 1 g, 2 g, 3 g and 4 g respectively. (Corresponding to Examples 1, 2, 3 and 4). Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] To address the technical problem of high density and large quality in some existing low-frequency absorbing materials, the main solution proposed in this application is as follows:

[0027] By preparing a metal ion solution, adding a gelling agent to the metal ion solution, magnetically stirring until homogeneous, and then heating it to boil, an aerogel layer is obtained.

[0028] The aerogel layer is heated until it comes to rest, thus obtaining a metal oxide aerogel;

[0029] By placing metal oxide aerogel and melamine powder into the upstream and downstream sides of a high-temperature tube furnace for high-temperature treatment, a medium-entropy alloy aerogel for in-situ growth of carbon nanotubes for microwave absorption can be obtained.

[0030] The medium-entropy alloy aerogel with in-situ grown carbon nanotubes for microwave absorption not only has superior microwave absorption performance, but also has low density and small mass, which can effectively avoid the drawbacks of existing microwave absorbing materials.

[0031] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0032] Example 1

[0033] This invention provides a medium-entropy alloy aerogel with in-situ grown carbon nanotubes for microwave absorption, the preparation method of which includes:

[0034] S1. Prepare 100 mL of solution with a total metal ion concentration of 0.1 mol·L⁻¹. -1 Multimetallic solutions, in which Ni 2+ Co 2+ Fe 3+ The mole ratio is 5:3:2.

[0035] In this embodiment, 1.454g Ni(NO3)2·6H2O, 0.873g Co(NO3)2·6H2O, and 0.808g Fe(NO3)3·9H2O were weighed and added sequentially to a beaker containing 100mL of deionized water solution. The beaker was placed on a heating platform and magnetically stirred at 50°C for 30 minutes until completely dissolved to obtain a metal ion solution.

[0036] S2. Weigh 0.45g of glycine (gelling agent) and add it directly to the metal ion solution (the molar ratio of glycine to nitrate is controlled at 3:5). Stir magnetically for 30 minutes until a homogeneous solution is obtained, then stop stirring. Remove the magnetic stir bar and heat the beaker to 200℃. After the solution boils and evaporates, a thick gel layer forms at the bottom of the beaker. Continue heating at high temperature until the gel spontaneously combusts, resulting in a large amount of dark brown fluffy sponge, which is the NiCoFe metal oxide aerogel.

[0037] S3. Take 0.1g of NiCoFe metal oxide aerogel into ceramic boat A. Weigh 1g of melamine powder into ceramic boat B. Place ceramic boat B in the upstream part of a high-temperature tube furnace and ceramic boat A in the downstream part of the high-temperature tube furnace. Assemble the tube furnace and slowly introduce a mixed gas (5% H2 and 95% Ar). Heat to 700℃ within 230min, hold for 6h, and cool to room temperature within 100min to obtain NiCoFe / CNT composite aerogel (i.e., medium-entropy alloy aerogel of in-situ grown carbon nanotubes for microwave absorption), denoted as FCNM-10 (its transmission electron microscopy image is shown below). Figure 1 ).

[0038] like Figure 2 As shown in (a) and (a'), the obtained FCNM-10 has an effective absorption bandwidth (stronger than -10dB is considered effective absorption) of 4.1GHz in the 2-18GHz range. Figure 3 As shown in (a), the effective absorption bandwidth (stronger than -4dB is considered effective absorption) in the 2-6GHz range is 2.8GHz. The density is 0.1g / cm³. 3 .

[0039] Example 2

[0040] This invention provides a medium-entropy alloy aerogel for in-situ growth of carbon nanotubes for microwave absorption. The difference between its preparation method and that of Example 1 is that the amount of melamine powder used in S3 is 2g, while the other steps remain unchanged. The resulting microwave absorbing material is denoted as FCNM-20.

[0041] like Figure 2 As shown in (b) and (b'), the obtained FCNM-20 has an effective absorption bandwidth of 3.5 GHz in the 2-18 GHz range, as... Figure 3 As shown in (b), the effective absorption bandwidth is 3.0 GHz in the 2-6 GHz range, and the density is 0.106 g / cm³. 3 .

[0042] Example 3

[0043] This invention provides a medium-entropy alloy aerogel for in-situ growth of carbon nanotubes for microwave absorption. The difference between its preparation method and that of Example 1 is that the amount of melamine powder used in S3 is 3g, while the other steps remain unchanged. The resulting microwave absorbing material is denoted as FCNM-30.

[0044] like Figure 2 As shown in (c) and (c'), the obtained FCNM-30 has an effective absorption bandwidth of 5.2 GHz in the 2-18 GHz range, as... Figure 3 As shown in (c), the effective absorption bandwidth is 3.6 GHz in the 2-6 GHz range, and the density is 0.11 g / cm³. 3 .

[0045] Example 4

[0046] This invention provides a medium-entropy alloy aerogel for in-situ growth of carbon nanotubes for microwave absorption. The difference between its preparation method and that of Example 1 is that the amount of melamine powder used in S3 is 4g, while the other steps remain unchanged. The resulting microwave absorbing material is denoted as FCNM-30.

[0047] like Figure 2 As shown in (d) and (d'), the obtained FCNM-40 has an effective absorption bandwidth of 0.1 GHz in the 2-18 GHz range, as... Figure 3As shown in (d), the effective absorption bandwidth is 2.6 GHz in the 2-6 GHz range, and the density is 0.113 g / cm³. 3 .

[0048] In this embodiment of the invention, electromagnetic parameters were obtained using a vector network analyzer. Paraffin wax was uniformly mixed with a prepared microwave absorbing material (15 wt%), melted under vacuum, and then pressed into coaxial ring samples with different thicknesses, each having an outer diameter of 7.0 mm and an inner diameter of 3.04 mm. The electromagnetic parameters of the coaxial ring samples were tested using a vector network analyzer (AV3629D). The minimum reflection loss (RL) for different thicknesses was fitted using transmission line theory formulas.

[0049]

[0050]

[0051] Z in Z0 is the effective input impedance, Z0 is the free space impedance, and ε is the effective input impedance. r and μ r These are the complex permittivity and complex permeability, respectively, and ε r =ε′-jε″,μ r =μ′-jμ″; where ε′ is the real part of the dielectric constant, ε″ is the imaginary part of the dielectric constant, μ′ is the real part of the permeability, μ″ is the imaginary part of the permeability, f is the frequency, d is the sample thickness, and c is the speed of light in vacuum.

[0052] This experiment calculated the microwave absorption performance of the absorbing material at thicknesses of 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, and 5 mm under different additive amounts. Plots were then generated based on the different additive amounts. Figure 2 and Figure 3 In the figure, each curve corresponds to the thickness of the corresponding absorbing material according to the label.

[0053] from Figure 2 The results show the changing trend of microwave absorption performance of the obtained microwave absorbing material in the 2-18 GHz range under different melamine addition amounts. With the gradual increase of melamine addition, the minimum reflection loss and effective absorption bandwidth first increase and then decrease. Figure 2 The area within the white dashed line in the middle a'-d' represents the effective absorption range, which generally increases first and then decreases.

[0054] from Figure 3 The results show the changing trend of microwave absorption performance of the obtained microwave absorbing material in the 2-6 GHz range under different melamine addition amounts. As the melamine addition amount gradually increases, the minimum reflection loss and effective absorption bandwidth first increase and then decrease.

[0055] The microwave absorbing material provided in this invention has excellent microwave absorption performance, mainly due to the following aspects:

[0056] First, the three-dimensional porous structure of the medium-entropy alloy aerogel skeleton in this composite material, which is made from in-situ grown carbon nanotubes, is beneficial to the dissipation of electromagnetic waves by multiple reflections and the interface polarization loss.

[0057] Secondly, the carbon nanotube array on this medium-entropy alloy aerogel composite material, which is made by in-situ growing carbon nanotubes, has good electrical conductivity, enabling electromagnetic waves to be converted into induced current and dissipated in the form of Joule heat.

[0058] Finally, the magnetic properties of the alloy aerogel on this medium-entropy alloy aerogel composite material, which is made from in-situ grown carbon nanotubes, combined with the conductivity of the carbon nanotubes, work synergistically to dissipate electromagnetic wave energy.

[0059] The obtained microwave absorbing material has a three-dimensional porous structure with low density and small mass, thus avoiding the defects of existing microwave absorbing materials.

[0060] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0061] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A medium-entropy alloy aerogel with in-situ grown carbon nanotubes for microwave absorption, characterized in that, The method for preparing the medium-entropy alloy aerogel with in-situ grown carbon nanotubes for microwave absorption includes: A multi-metal solution with a total metal ion concentration of 0.1 mol / L was prepared; the multi-metal solution was composed of a mixture of Ni(NO3)2·6H2O, Co(NO3)2·6H2O and Fe(NO3)3·9H2O; the multi-metal solution contained Ni 2+ Co 2+ Fe 3+ The mole ratio is 5:3:2; A gelling agent was added to a multi-metal solution, and the mixture was stirred magnetically until homogeneous to obtain a solution; the molar ratio of the gelling agent to nitrate was 3:

5. The mixture is heated to boil and evaporate to obtain a gel layer; the gel layer is further heated until it spontaneously combusts to obtain a NiCoFe metal oxide aerogel. The obtained NiCoFe metal oxide aerogel was placed in ceramic boat A, and melamine powder was weighed into ceramic boat B. Place ceramic boat A in the downstream part of the high-temperature tube furnace and ceramic boat B in the upstream part of the high-temperature tube furnace. Assemble the high-temperature tube furnace, slowly introduce protective gas, raise the temperature to 700°C within 230 minutes, hold for 6 hours, and cool to room temperature within 100 minutes to obtain the medium-entropy alloy aerogel of in-situ grown carbon nanotubes for microwave absorption.

2. The medium-entropy alloy aerogel with in-situ grown carbon nanotubes for microwave absorption according to claim 1, characterized in that, The gelling agent is glycine.

3. The medium-entropy alloy aerogel with in-situ grown carbon nanotubes for microwave absorption according to claim 1, characterized in that, The protective gas comprises 5% H2 and 95% Ar.

4. The medium-entropy alloy aerogel with in-situ grown carbon nanotubes for microwave absorption according to claim 1, characterized in that, The mass ratio of NiCoFe metal oxide aerogel placed in ceramic boat A to melamine powder placed in ceramic boat B is 1:10 to 40.

5. The medium-entropy alloy aerogel with in-situ grown carbon nanotubes for microwave absorption according to claim 4, characterized in that, The mass ratio of NiCoFe metal oxide aerogel placed in ceramic boat A to melamine powder placed in ceramic boat B is 1:

10.

6. The medium-entropy alloy aerogel with in-situ grown carbon nanotubes for microwave absorption according to claim 4, characterized in that, The mass ratio of NiCoFe metal oxide aerogel placed in ceramic boat A to melamine powder placed in ceramic boat B is 1:

20.

7. The medium-entropy alloy aerogel with in-situ grown carbon nanotubes for microwave absorption according to claim 4, characterized in that, The mass ratio of NiCoFe metal oxide aerogel placed in ceramic boat A to melamine powder placed in ceramic boat B is 1:

30.

8. The medium-entropy alloy aerogel with in-situ grown carbon nanotubes for microwave absorption according to claim 1, characterized in that, The heating temperature for boiling and evaporating the mixture is 200°C.

Images